1. Field of the Invention
Embodiments of the present disclosure relate to synchronizing audio signals, and particularly to a system and method for synchronizing audio signals of a communication device.
2. Description of Related Art
Wireless communication systems are primarily designed for bidirectional audio communication. In a wireless communication system with voice service, a communication device, such as a mobile phone, needs to simultaneously process audio signals in two different directions such as uplink and downlink. The uplink data are audio signals recorded by a receiver microphone of the communication device, while the downlink data are audio signals transmitted from the other end of the wireless communication network to the receiver, and further played back by a speaker of the receiving communication device.
In a communication system with voice services, echoing is a common quality-degrading occurrence. An echo occurs when sound created at the originating end reflects back to and is received by at the originating end. In a wireless communication system, a major source of echoing is sound played by the speaker of the receiving communication device reflecting back to the originating end via the microphone at the receiving end. Essentially, the uplink audio signals include the downlink audio signals embedded therein. Therefore, it is necessary to estimate the echo by an echo cancellation program (ECP), eliminate the estimated echo from the received audio signals at the receiver microphone, and then transmit outgoing audio signals to the other end of the wireless communication network. In other words, the ECP finds the downlink audio signals portion in the uplink audio signals, that is the echo, and removes or suppresses that portion of the signal.
The ECP is commonly designed and implemented in hardware or software. The ECP implemented in hardware in a communication device removes echo portion from received audio signals at the microphone. The hardware implementation, while providing a good solution to echo cancellation, concurrently increases hardware cost and volume, impacting portability of the communication device.
Implementation of the ECP via software, while effectively removing the echo portion from received audio signals at a receiver microphone, requires uplink audio signals to be processed before the downlink audio signals since. The uplink audio signal is recorded by the receiver microphone of the communication device, the downlink audio signal is recorded by the communication device at the other end, and the downlink audio signal is further played back after transmission via the communication network. Effectively, the ECP software records the downlink audio signals as the echo portion to storage and removes the echo portion from the uplink audio signals. The communication device consequently requires two processors to support the implementation, one processor specifically processing the ECP, allowing simultaneous processing of the echo at the receiver microphone, and the other processor driving main operating system (OS) functionality. The requirement for an additional processor, as before, increases hardware cost and impacts portability of the communication device.
Therefore, what is needed is a system and method for synchronizing the audio signals of a communication device removing the downlink audio signals from the uplink audio utilizing a single processor.